The overall ratings of seven Biotechnology stocks are down on Portfolio Grader this week. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, Genomic Health, Inc. (NASDAQ:GHDX) falls to a D (“sell”), worse than last week’s grade of C (“hold”). Genomic Health is a life science company, which is focused on the development and commercialization of genomic-based clinical diagnostic tests for cancer that allow physicians and patients to make individualized treatment decisions. For Portfolio Grader’s specific subcategory of Earnings Revisions, GHDX also gets an F. The trailing PE Ratio for the stock is 821.00. For a full analysis of GHDX stock, visit Portfolio Grader.

This week, Acorda Therapeutics, Inc. (NASDAQ:ACOR) drops from a C to a D rating. Acorda Therapeutics is a commercial stage biopharmaceutical company dedicated to the identification, development and commercialization of novel therapies that improve neurological function in people with multiple sclerosis (MS), spinal cord injury and other disorders of the central nervous system. The stock gets F’s in Earnings Revisions and Sales Growth. For more information, get Portfolio Grader’s complete analysis of ACOR stock.

This week, Amarin Corporation Plc Sponsored ADR’s (NASDAQ:AMRN) rating worsens to a D from the company’s C rating a week ago. Amarin focuses on developing the treatment for cardiovascular disease in the field of lipid science. The stock gets F’s in Earnings Growth, Earnings Revisions, Equity, and Cash Flow. As of Sept. 10, 2013, 13.2% of outstanding Amarin Corporation Plc Sponsored ADR shares were held short. Shares of the stock have been trading at an exceptionally rapid pace, up twofold from the week prior. To get an in-depth look at AMRN, get Portfolio Grader’s complete analysis of AMRN stock.

Exelixis, Inc. (NASDAQ:EXEL) ratings are on the decline this week as the company earns an F (“strong sell”). Last week, it received a D (“sell”). Exelixisis a development-stage biotechnology company dedicated to the discovery and development of small-molecule therapeutics for the treatment of cancer and other serious diseases. The stock gets F’s in Earnings Growth, Earnings Momentum, and Equity. Margin Growth and Sales Growth also get F’s. As of Sept. 10, 2013, 21.9% of outstanding Exelixis, Inc. shares were held short. For a full analysis of EXEL stock, visit Portfolio Grader.

Trius Therapeutics, Inc. (NASDAQ:TSRX) is having a tough week. The company’s rating falls from a C to a D. Trius Therapeutics is a biopharmaceutical company. The stock receives F’s in Earnings Growth, Earnings Momentum, and Equity. Cash Flow and Sales Growth also get F’s. Shares of the stock have been changing hands at an unusually rapid pace, three times the rate of the week prior. For more information, get Portfolio Grader’s complete analysis of TSRX stock.

Discovery Laboratories, Inc. (NASDAQ:DSCO) earns a D this week, moving down from last week’s grade of C. Discovery Laboratories is a biotechnology company focused on developing products for the treatment of respiratory disease. The stock gets F’s in Equity and Cash Flow. Shares of the stock are being traded at a very rapid pace, up 525.3% from the week prior. For a full analysis of DSCO stock, visit Portfolio Grader.

Achillion Pharmaceuticals, Inc.’s (NASDAQ:ACHN) rating weakens this week, dropping to a D versus last week’s C. Achillion focuses on the discovery, development and commercialization of innovative treatments for infectious diseases. The stock also rates an F in Equity. As of Sept. 10, 2013, 15.1% of outstanding Achillion Pharmaceuticals, Inc. shares were held short. Shares of the stock have been exchanging at an usually rapid pace, twice the rate of the week prior. To get an in-depth look at ACHN, get Portfolio Grader’s complete analysis of ACHN stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.